I'm pretty sure there are a bunch of guys around here who can get absolutely great results with whatever machines and methods they're using.
There are advantages and disadvantages to every method. There are ways to screw up and waste time associated with every machine. Once you get a finish with no visible defects, you've gotten where you need to go. Then the question is, how long does it take to get there? How long is that finish going to last, fillers dry out and wash out while truly finished paint will have to be scratched to look bad again. Are we thinning the paint to much in defect removal or do we know when to stop? Personally, I almost never go for perfect unless it's on a show car. For me, again, it's about good value for money. I'd rather leave a deep scratch and thicker paint around it than take out the scratch and leave the paint so thin it won't be able to handle another scratch. That's why I only use my rotary one time on most cars. After that, it's the dual action only.
If I were going to advise someone starting out, I'd say get a true dual action like the Makita BO6040 and learn to use it. That machine is more than aggressive enough with the right polish and pad and it's safe enough that most people who will spend that kind of money will be serious enough and attentive enough to stay out of trouble.
Finally, I think it's time well spent watching people who are getting good results and trying to learn as much from them as possible. I'll teach anyone who wants to know exactly how I get the results I do, with the understanding that they leave my clients alone from then on of course.
Merry Christmas,
Robert